I'm so sorry to hear about your mom. I lost my mom on August 17, 2007. It is very difficult to hear the words that there is nothing more that can be done. My mother did not survive long (only about a week) when hospice was called. I know people pre plann funerals, but we did not. We knew, in the back of our minds, what we would like to happen. The funeral director took excellent care of us, so we didn't feel overwhelmed. We were extremely sad, but not overwhelmed. I have 2 suggestions for you. One is to know what organization you want donations to be made in your mom's memory for the obituary. And the other is if you are planning a mass or church service, have an idea of what songs you would want. You can google funeral songs on line if you are unsure.
God bless you, your family, and your mom at this difficult time.